1. Field of the Invention
The present invention relates to an apparatus and a method for driving a plasma display panel (PDP). More specifically, the present invention relates to an apparatus and a method for driving a PDP, where a switch device can perform zero voltage switching in driving the PDP.
2. Description of the Related Art
In general, a PDP is a flat plate display for displaying characters or images using plasma generated by gas discharge. Pixels ranging from hundreds of thousands to more than millions are arranged in the form of a matrix according to the size of the PDP. PDPs are divided into direct current (DC) PDPs and alternating current (AC) PDPs according to the shape of the waveform of an applied driving voltage and the structure of a discharge cell.
The most significant difference between the DC PDP and the AC PDP lies in that current directly flows in discharge spaces while a voltage is applied in the DC PDP, because electrodes are exposed to the discharge spaces. Therefore, a resistor for restricting the current must be used outside of the DC PDP. On the other hand, in the case of the AC PDP, the current is restricted due to the natural formation of capacity because a dielectric layer covers the electrodes. The AC PDP has a longer life than the DC PDP because the electrodes are protected against the shock caused by ions during discharge. A memory characteristic that is one of the important characteristics of the AC PDP is caused by the capacity due to the dielectric layer that covers the electrodes.
According to the light emission principle of the AC PDP, discharge occurs because an electric potential difference in the form of a pulse is formed in common electrodes (X electrodes) and scan electrodes (Y electrodes). As such, vacuum ultraviolet (UV) rays generated in a discharge process are excited to red R, green G, and blue B fluorescent bodies. The respective fluorescent bodies emit light due to light combination.
In the AC PDP, because the X electrodes and the Y electrodes for sustaining discharge operate as capacitive loads, capacitance Cp with respect to the X and Y electrodes exists. Reactive power other than power for discharge is necessary in order to apply waveforms for the sustain-discharge. A circuit for recovering and re-using the reactive power is referred to as a sustain-discharge circuit, or a power recovery circuit.
According to the method for driving the panel by the X and Y electrode driving circuits, a frame consists of n sub-fields. A sub-field consists of a reset period, a scan period, a sustain period, and an erase period.
In the reset period, the address electrodes A1 through Am and the X electrodes are sustained to be at 0 V in the first half thereof. A voltage of more than a discharge starting voltage to a voltage of no more than the discharge starting voltage with respect to the sustain electrodes is applied to the Y electrodes. In the latter half of the reset period, the voltage of no more than the discharge starting voltage with respect to the sustain electrodes is applied to the scan electrodes. In the scan period, the scan electrodes are sustained to be at a scan voltage. A positive scan pulse voltage and a scan pulse voltage (0 V) are simultaneously applied to the address electrode corresponding to the discharge cell to be displayed in the first line among addressing electrodes and the scan electrode in the first line, respectively, so that the wall charge is accumulated. In the sustain period, a predetermined sustain pulse is applied to the scan and sustain electrodes so that the sustain-discharge occurs in gray scales to be displayed in the discharge cells. In the erase period, a predetermined erase pulse is applied to the sustain electrodes so that the sustain-discharge is stopped.
Driving of the sustain-discharge circuit of a conventional AC PDP will now be described with reference to FIGS. 1A and 1B that show a conventional sustain-discharge circuit and the operation waveforms of the conventional sustain-discharge circuit.
As shown in FIG. 1A, the sustain-discharge circuit suggested by L. F. Weber and disclosed in the U.S. Pat. Nos. 4,866,349 and 5,081,400, is the sustain-discharge circuit or the power recovery circuit of the AC PDP. In the driving circuit of the AC PDP, a sustain-discharge circuit 10 of the X electrodes has the same structure as that of a sustain-discharge circuit 11 (not shown in detail) of the Y electrodes. The sustain-discharge circuit of the X electrodes will now be described for sake of convenience.
The conventional sustain-discharge circuit 10 includes a power recovery unit comprising two switches S1 and S2, two diodes D1 and D2, and a power recovery capacitor Cc and a sustain-discharge unit comprising two serially connected switches S3 and S4. An inductor Lc is connected between the diodes D1 and D2 of the power recovery unit and the two switches S3 and S4 of the sustain-discharge unit. A load having a capacitor Cp of the PDP is connected to the sustain-discharge unit. At this juncture, a parasitic device is not displayed.
The conventional sustain-discharge circuit having the above structure operates in four modes according to the switching sequence operations of the switches S1 through S4, as shown in FIG. 1B. The waveforms of the current IL that flows through an output voltage Vp and the inductor Lc are respectively shown according to the switching sequence operations.
In an initial stage, the panel both-end voltage is sustained to be 0 V because the switch S4 is made to turn on just before the switch S1 is made to turn on. As such, the power recovery capacitor Cc is previously charged by a voltage Vs/2 that is half of an external applied voltage Vs so that a rush current is not generated when the sustain-discharge starts.
In a state where the panel both-end voltage Vp is sustained to be 0 V, at the point of time t0, the operation of a mode 1 where the switch S1 is turned on and the switches S2, S3, and S4 are turned off, starts.
In the operation periods between t0 and t1 of the mode 1, an LC resonance circuit is formed through the channel of the power recovery capacitor Cc, the switch S1, the diode D1, the inductor Lc, and the plasma panel capacitor Cp. Therefore, the current IL flows through the inductor Lc and the output voltage Vp of the panel increases.
As shown in FIG. 1B, the current IL that flows through the inductor LC slowly decreases due to parasitic resistance (not shown) and becomes 0 at the point of time t1. The output voltage Vp of the panel becomes the external applied voltage Vs.
When the mode 1 is completed, a mode 2, where the switches S1 and S3 are turned on and the switches S2 and S4 are turned off, starts. In the operation period between t1 and t2 of the mode 2, the external applied voltage Vs directly flows through the panel capacitor Cp through the switch S3, to thus sustain the output voltage Vp of the panel.
When the mode 2 is completed in a state where the discharge of the output voltage Vp of the panel is sustained, a mode 3, where the switch S2 is turned on and the switches S1, S3, and S4 are turned off, starts.
In the operation period between t2 and t3 of the mode 3, the LC resonance circuit is formed through the channel reverse to that in the mode 1, that is, through the channel of the plasma panel capacitor Cp, the inductor Lc, the diode D1, the switch S2, and the power recovery capacitor Cc. Accordingly, as shown in FIG. 1B, the current IL flows through the inductor Lc and the output voltage Vp of the panel decreases. Therefore, the current IL of the inductor Lc and the output voltage Vp of the panel become 0 at the point of time t3.
In the operation period between t3 and t4 of a mode 4, the switches S2 and S4 are turned on and the switches S1 and S3 are turned off. Accordingly, the output voltage Vp of the panel is sustained to be 0 V. When the switch S1 is turned on again in this state, the process returns to the operation of the mode 1. Accordingly, the operations are repeated thereinafter.
In the conventional sustain-discharge circuit 10, because the number of the switches of the power recovery unit of the entire sustain-discharge circuit (including the X and Y electrode driving circuits) is four, the structure of an operation driver is complicated. Because a high-priced switch device is used, it is difficult to realize a low-priced sustain-discharge driving circuit.
In addition, it is not possible for the switches that form the circuit to perform the zero voltage switching due to the parasitic components of the driving circuit such as the parasitic resistance of the inductor, the parasitic resistances of the capacitor and the panel, and the conductance resistance of the switch. Accordingly, switching loss significantly increases when the switches are turned on.
Also, a significantly large rush current is generated when a sustain pulse starts in a state where the power recovery capacitor Cc is not charged to the voltage Vs/2 right after the light emission starts.
It is an object of the present invention to provide a sustain-discharge circuit of a PDP, wherein a sustain-discharge circuit can be operated by a switch, an operation switch that forms the sustain-discharge circuit can perform zero voltage switching, and a rush current can be prevented without an additional external protecting circuit just after light emission starts.
In order to achieve the above object, in an embodiment of the present invention, there is provided an apparatus and a method for driving a PDP including a plurality of address electrodes, a plurality of scan electrodes and sustain electrodes arranged in a zig-zag pattern so as to make pairs with each other, and a panel capacitor formed by the scan electrodes and the sustain electrodes.
In one aspect of an embodiment of the present invention, there is provided an apparatus for driving a PDP including a sustain-discharge unit and first and second charge and discharge units. The sustain-discharge unit includes first and second switches, which are serially connected to each other between a power source to which a sustain-discharge voltage is applied and a ground, and whose contact point is connected to one end of the panel capacitor; and third and fourth switches, which are serially connected to each other between the power source and the ground and whose contact point is connected to the other end of the panel capacitor. The first charge and discharge unit includes a first inductor whose one end is coupled to one end of the panel capacitor, and which increases the voltage of the panel capacitor to the first sustain-discharge voltage using a resonance of the first inductor and the panel capacitor. The second charge and discharge unit includes a second inductor whose one end is coupled to the other end of the panel capacitor, and which decreases the voltage of the panel capacitor to the second sustain-discharge voltage using a resonance of the second inductor and the panel capacitor.
At this time, the sustain-discharge unit drives the first switch during resonance of the first inductor, to thus sustain the first sustain-discharge voltage, and drives the third switch during resonance of the second inductor, to thus sustain the second sustain-discharge voltage.
In a second aspect of an embodiment of the present invention, there is provided an apparatus for driving a PDP including first through sixth switches, first and second inductors, and first and second diodes. The first and second switches are serially connected to each other between a power source to which a sustain-discharge voltage is applied and a ground and a contact point thereof is connected to one end of the panel capacitor. The third and fourth switches are serially connected to each other between the power source and the ground, and a contact point thereof is connected to the other end of the panel capacitor. The first inductor has one end coupled to one end of the panel capacitor, and the second inductor has one end coupled to the other end of the panel capacitor. The fifth and sixth switches are respectively connected between the power source and the other end of the first inductor, and between the power source and the other end of the second inductor. The first and second diodes are respectively connected between the other end of the first inductor and the ground, and between the other end of the second inductor and the ground.
In a third aspect of an embodiment of the present invention, there is provided an apparatus for driving a PDP including first through eighth switches, first and second inductors, and first through fourth diodes. The first and second switches are serially connected to each other between a power source to which a sustain-discharge voltage is applied and a ground, and a contact point thereof is connected to one end of the panel capacitor. The third and fourth switches are serially connected to each other between the power source and the ground, and a contact point thereof is connected to the other end of the panel capacitor. The first inductor has one end coupled to one end of the panel capacitor, and the second inductor has one end coupled to the other end of the panel capacitor. The fifth and sixth switches are serially connected to each other between the power source and the ground, and a contact point thereof is connected to the other end of the first inductor. The seventh and eighth switches are serially coupled to each other between the power source and the ground, and a contact point thereof is connected to the other end of the second inductor. The first and second diodes are serially connected to each other between the power source and the ground in a backward direction, and a contact point thereof is connected to the other end of the first inductor. The third and fourth diodes are serially connected to each other between the power source and the ground in a backward direction, and a contact point thereof is connected to the other end of the second inductor.
In fourth through seventh aspects of an embodiment of the present invention, there is provided a method for driving a PDP including a plurality of address electrodes, a plurality of scan electrodes and sustain electrodes arranged in a zig-zag pattern so as to make pairs with each other, a panel capacitor formed by the scan electrodes and the sustain electrodes, first and second switches, which are serially connected to each other between a power source for supplying a sustain-discharge voltage and a ground, and whose contact point is connected to one end of the panel capacitor, third and fourth switches, which are serially connected to each other between the power source and the ground and whose contact point is connected to the other end of the panel capacitor, and first and second inductors connected to one end and to the other end of the panel capacitor.
In a fourth aspect of an embodiment of the present invention, according to a method for driving a PDP, the voltage of the panel capacitor increases to a first sustain-discharge voltage using a resonance generated by the panel capacitor and the first inductor due to the driving of the fourth switch and a fifth switch connected between the power source and the first inductor. The first and fourth switches are driven during the resonance to thus sustain the voltage of the panel capacitor to be at the first sustain-discharge voltage. The voltage of the panel capacitor decreases to a second sustain-discharge voltage using resonance generated by the panel capacitor and the second inductor due to the driving of the second switch and a sixth switch connected between the power source and the second inductor. The second and third switches are driven during the resonance to thus sustain the voltage of the panel capacitor to be at the second sustain-discharge voltage.
In a fifth aspect of an embodiment of the present invention, according to a method for driving a PDP, the voltage of the panel capacitor increases to a first sustain-discharge voltage using a resonance generated by the panel capacitor and the first and second inductors due to the driving of a fifth switch connected between the power source and the first inductor, and a sixth switch connected between the second inductor and the ground. The fifth and sixth switches are turned off during the resonance and driving of the first and fourth switches to thus sustain the voltage of the panel capacitor to be at the first sustain-discharge voltage. The voltage of the panel capacitor decreases to a second sustain-discharge voltage using a resonance generated by the panel capacitor and the first and second inductors due to the driving of a seventh switch connected between the power and the second inductor, and an eighth switch connected between the first inductor and the ground. The seventh and eighth switches are turned off during the resonance and driving of the second and third switches to thus sustain the voltage of the panel capacitor to be at the second sustain-discharge voltage.
In a sixth aspect of an embodiment of the present invention, according to a method for driving a PDP, first and fourth switches are driven to thus sustain the voltage of the panel capacitor to be at a first sustain-discharge voltage. Fifth and sixth switches, respectively connected between the ground and the first inductor and between the second inductor and the power source, are additionally driven to thus inject current into the first and second inductors in a state where the voltage of the panel capacitor is sustained to be at the first sustain-discharge voltage. The first, fourth, fifth, and sixth switches are turned off to thus decrease the voltage of the panel capacitor to a second sustain-discharge voltage using resonance generated by the first and second inductors and the panel capacitor. The second and third switches are driven to thus sustain the voltage of the panel capacitor to be at the second sustain-discharge voltage. Seventh and eighth switches, respectively connected between the power source and the first inductor and between the second inductor and the ground, are additionally driven to thus inject current into the first and second inductors in a state where the voltage of the panel capacitor is sustained to be at the second sustain-discharge voltage. The second, third, seventh, and eighth switches are turned off to thus increase the voltage of the panel capacitor to a first sustain-discharge voltage using resonance generated by the first and second inductors and the panel capacitor.
In a seventh aspect of an embodiment of the present invention, according to a method for driving a PDP, fifth and sixth switches, respectively connected between the power source and the first inductor and between the second inductor and the ground are driven to thus inject current into the first and second inductors in a state where the voltage of the panel capacitor is sustained to be at a first sustain-discharge voltage by the driven second and third switches. The second and third switches are turned off to thus increase the voltage of the panel capacitor to a second sustain-discharge voltage using resonance generated by the first and second inductors and the panel capacitor. The fifth and sixth switches are turned off and the first and fourth switches are driven to thus sustain the voltage of the panel capacitor to be at the second sustain-discharge voltage. Seventh and eighth switches, respectively connected between the first inductor and the ground and between the power source and the second inductor, are additionally driven to thus inject current into the first and second inductors in a state where the voltage of the panel capacitor is sustained to be at the second sustain-discharge voltage. The first and fourth switches are turned off, to thus decrease the panel capacitor to the first sustain-discharge voltage using resonance generated by the first and second inductors and the panel capacitor. The seventh and eighth switches are turned off and the second and third switches are driven to thus sustain the voltage of the panel capacitor to be at the first sustain-discharge voltage.